Originally posted by GUB You won't forget they are there once you get some Manual focus lenses.
This is a cut and paste from another thread. It explains focus peaking quite well to me.
" I first discovered focus peaking when I purchased my K-01, and I find it an invaluable tool. If you always use a DSLR and always use the optical viewfinder when taking pictures then you probably won't need focus peaking. But, if you use live view on your DSLR, or have a mirrorless camera such as the K-01 or any of the Q series, then focus peaking is very useful indeed. Basically it makes it very easy to manually adjust your lens to ensure that the exact part of the subject that you wish to be in focus, is in focus. The camera screen shows a white highlighted fringe around portions of the subject that are focussed, and turning the focus ring on your lens moves the effect around the subject giving you a live visual indication of the depth of focus. It's a really useful, accurate tool, and one that I use a great deal. It's especially handy for me on the K-01 when mounting older manual lenses. Using them becomes a breeze. I see that Steve doesn't get on well with it, but everyone has their own styles and preferences, and for me, with my lenses, it works brilliantly. "
Read more at:
What is focus peaking? - PentaxForums.com